EVOH Resin Composition Stabilizing Metal Ions to Prevent Yellowing
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Solution Overview
Problem
Conventional ethylene-vinyl alcohol copolymer (EVOH) compositions suffer from yellowing and deterioration in appearance characteristics during melt molding, especially at high temperatures, which affects the quality of multilayered structures and long-run workability.
Innovation Solution
A resin composition containing an ethylene-vinyl alcohol copolymer, a multivalent carboxylic acid or carboxylate ion, and a metal ion, with specific molar ratios and functional groups, which inhibits yellowing and improves interlayer adhesiveness and long-run workability by stabilizing the metal ion and preventing catalytic reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metal salt is contained in an EVOH composition to improve adhesiveness between layers in multilayered structures, then interlayer adhesiveness is improved, but yellowing occurs more likely and appearance characteristics are deteriorated
Solution Approach 1:
A chelating agent is introduced as an intermediary substance that forms a complex with the metal salt, preventing the metal ions from catalyzing the yellowing reaction while still allowing them to provide adhesion promotion. The chelating agent mediates between the metal salt's beneficial adhesion effect and its harmful yellowing effect.
Solution Approach 2:
The harmful yellowing effect caused by metal salts is converted into a benefit by using the metal ions' coordination ability with chelating agents. The same metal ions that cause yellowing when free are now utilized in a coordinated state to provide both adhesion and prevent yellowing simultaneously.
2Adaptability or versatility
If melt molding is carried out at high temperature over 200°C to enable co-extrusion with other thermoplastic resins, then multilayered structure formation is enabled, but yellowing is more likely to occur
Solution Approach 1:
The chelating agent acts as a protective intermediary that stabilizes metal ions during high-temperature processing, preventing them from catalyzing degradation reactions. This allows the material to withstand the high temperatures required for co-extrusion without yellowing.
Solution Approach 2:
The chemical environment parameters are changed by introducing the chelating agent, which alters the coordination state of metal ions and their reactivity. This parameter change allows the system to maintain stability at higher temperatures that would otherwise cause yellowing.
3Manufacturing precision
If an EVOH is exposed to high temperature such as no lower than 260°C during co-extrusion with thermoplastic resin, then multilayered structure is obtained, but yellowing occurs
Solution Approach 1:
The chelating agent serves as a protective intermediary that forms a stable complex with metal ions, preventing them from catalyzing yellowing reactions even at temperatures of 260°C or higher. This intermediary protection enables high-temperature processing without quality degradation.
4Productivity
If EVOH is reused repeatedly by recovering and reusing edge parts of molded products, then material utilization is improved, but deterioration of EVOH proceeds and defects such as gels and seeds increase
Solution Approach 1:
The chelating agent provides beforehand protection by stabilizing metal ions before they can catalyze degradation reactions during repeated processing. This prior cushioning effect prevents the accumulation of defects that would normally occur with repeated reuse of the material.
Solution Approach 2:
The chelating agent acts as a sacrificial protective component that prevents the degradation of the valuable EVOH polymer. By protecting the main material, it enables repeated reuse that would otherwise be limited by rapid deterioration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composition effectively prevents yellowing and enhances appearance characteristics and interlayer adhesiveness, even at high temperatures, resulting in superior melt molding performance and recyclability of multilayered structures.
Implementation Method 1
a multivalent carboxylic acid or carboxylate ion, and a metal ion, with specific molar ratios and functional groups, which inhibits yellowing and improves interlayer adhesiveness and long-run workability by stabilizing the metal ion and preventing catalytic reactions
Data Source
Figure 1
AI summary
An object of the present invention is to provide an EVOH-containing resin composition which has superior appearance characteristics and long-run workability in melt molding and enables occurrence of yellowing etc. , in melt molding to be inhibited particularly, even in melt molding at high temperatures of, for example, no less than 260°C. Further provided is a multilayered structure molded from the composition. The present invention provides a resin composition containing (A) an ethylene-vinyl alcohol copolymer, (B) a carboxylic acid and/or a carboxylate ion, and (C) a metal ion, wherein the component (B) includes (B2) a multivalent carboxylic acid and/or a multivalent carboxylate ion, and the molar ratio (B2/C) of the multivalent carboxylic acid and the multivalent carboxylate ion (B2) to the metal ion (C) is 0.002 or greater and 2 or less.